The structure of the parity-doublet bands in 231Pa

The level structure of 231Pa was investigated by means of the 231Pa(d,d'), 231Pa(p,p') and 232Th(p,2nγ) reactions and Coulomb excitation and by means of the electron-capture decay of 231U to 231Pa. Two low-lying opposite-parity bands based on the Kπ=1/2± states were observed up to spins 31/2- and 21/2+, respectively. From the E1/E2 branching ratios the intrinsic electric dipole moment was determined to be vertical stroke D0 vertical stroke ∼0.04 e.fm. Weak Coulomb excitation of other bands was observed. The structure of 231Pa is compared to that of 229Pa, in particular with regard to octupole effects. The level scheme and transition intensities in Coulomb excitation are analyzed in the framework of the quasiparticle+phonon model. (orig.)